1. Field of Invention
This invention relates generally to manually-operated, multi-constituent dispensers, and more particularly to a dispenser in which the constituents are metered and then intermixed before being discharged to yield a composition in which the relative proportions of the constituents are settable by the user.
2. Status of Prior Art
Multi-constituent dispensers are known in which the constituents are separately stored and are intermixed before being discharged. Thus, the Moskowitz U.S. Pat. No. 3,031,104 shows a dispenser in the form of a squeeze tube divided into separate compartments, one containing a toothpaste and the other a germicidal agent which if intermixed and stored with the paste would in time result in deterioration of the toothpaste. When the Moskowitz dispenser tube is squeezed, the two constituents are then fed into a mixing chamber before being discharged as a mixture.
Along similar lines is the multi-compartment squeeze tube disclosed in the Cella U.S. Pat. 3,581,940 in which the compartments contain interactive fluid components and therefore must be packaged separately (such as constituents which when intermixed form a hair color preparation). In Cella, when the tube is squeezed, the liquids are then intermixed before being discharged.
In the Cella and Moscowitz patents, the volumetric ratio of the ingredients forming the mixture is predetermined by the parameters of the squeeze tube compartments, and therefore cannot be controlled by the user. A similar limitation exists in the two-component epoxy glue dispenser disclosed in the Wagenhals U.S. Pat. No. 3,029,983 in which the two components are stored in separate squeeze tubes having different transverse dimensions. These tubes are placed in a case under a pressure roller turned by a knob. As the roller is advanced, the glue components are concurrently extruded from the tubes in a ratio predetermined by the relative dimensions of the tubes.
The Ryder U.S. Pat. No. 4,736,872 shows separate flexible storage pouches containing different ingredients to be dispensed. Ryder's concern is with tinting of soft contact lens, and for this purpose, he provides a dispenser in which the fluids contained in the pouches are discharged in sequence to carry out a lens tinting operation.
The concern of the present invention is with a multi-constituent composition in which the relative proportions of the constituents determine the effective strength or other characteristic of the composition, and in which the characteristic must be appropriate to a given application. While the invention will be described as a dispenser for a sunscreen lotion composed of three intermixed constituents, it is to be understood that it is generally applicable to drugs or other compositions having at least two constituents which are not to be intermixed until the dispenser is actuated.
As noted in the article by Shaath, "The Chemistry of Sunscreens," that appeared in the Mar. 1986 issue of Cosmetics and Toiletries (pages 55 to 69), over a half million new cases of skin cancer a year are reported in the United States. The principal cause of such cancer is excessive exposure to damaging ultraviolet rays emanating from the sun.
Ultraviolet rays induce photochemical reactions harmful to the skin. The most damaging are those in the UV-A region (320-400 nm), those in the UV-B region (290-320 nm), and also those in the UV-C region (200-290 nm). Rays in the UV-C region normally need not be taken into account in sunscreens, for these deleterious rays are filtered out by the ozone layer in the stratosphere. But rays in the UV-A and UV-B regions are not filtered out by the ozone layer. The present invention is not, however, limited to sunscreens which are effective only with respect to rays in the UV-A and UV-B regions, for large gaps which have developed in the ozone layer in certain areas of the world, as a consequence of industrial air pollution and other factors, make it now necessary in these areas to provide sunscreens effective against UV-C rays.
The function of a conventional sunscreen lotion is mainly to shield the skin from radiation in the UV-B region, for these rays penetrate the skin and may cause severe burning or erythema. Limited radiation from the UV-A region is permitted to penetrate the skin, for these rays act to stimulate the formation of melanin which produces a tan and acts as a defense against burning. But excessive exposure to UV-A rays can also be damaging to the skin.
Sunscreen chemicals are of two types. One acts as a physical blocker which tends to reflect and scatter harmful UV radiation. Among chemicals which function as physical blocks are titanium oxide and petrolatum. The other type is a chemical absorber such as PABA and actyl salicylate that tends to absorb harmful radiation (both UV-A and UV-B) to render these innocuous.
The effectiveness of a sunscreen is currently graded by its Sun Protection Factor or SPF. This rating system indicates the number of hours of sun exposure equivalent to one hour of unprotected sun exposure. Thus an SPF-8 gives eight hours of exposure with protection equivalent to one hour of unprotected exposure. The useful SPF range is SPF-2 to SPF-12 or higher; the lowest value affording minimum protection and the highest, maximum protection.
The practical problem experienced by the typical consumer with a standard sunscreen lotion is that a given SPF rating is not effective under all circumstances; for while this rating may be adequately protective, say, in the early morning hours, it may be altogether inadequate toward noon or in the early afternoon. Moreover, individuals differ from each other not only in their natural skin color and in their sensitivity to ultraviolet radiation, but also in their objectives in regard to tanning. Thus some individuals wish to enhance their appearance by acquiring a deep tan without burning, while others are more concerned with possible skin damage and seek to minimize tanning even after many hours of exposure.
In order to provide sunscreens that satisfy the requirements of diverse individuals and accommodate quotidian changes in the intensity of the sun, it would normally be necessary to provide these individuals with a set of sun screen lotions each having different SPF ratings in the 2 to 12 range.
Thus if a family of seven were to go to the beach on a hot summer day, in order to protect the parents and children from the damaging effects of sun exposure and to meet their individual SPF requirements in the course of the day, even six sunscreen lotions having different SPF ratings may not be sufficient for this purpose. And it goes without saying that the need to bring along six sunscreen dispensers to the beach in addition to all of the other articles a family normally has to carry represents a practical drawback. It is more likely that no more than two or three lotions having different SPF ratings will be taken to the beach.
Because of the danger of premature aging of the skin and the risk of skin cancer resulting from excessive exposure to UV radiation, the need exists for a single sunscreen dispenser yielding an SPF grade appropriate to the prevailing intensity of the sun and to the skin of the individual being exposed.